Backspacing mechanism



@t. 14, 1952 c. L. BOSSMEYER 2,613,938

BACKSPACING MECHANISM Filed Sept. 13, 1947 4 Sheets-Sheet l I N a a (Y)mvzmoa N Charles L. Bossmeyer BY W340 0% M, 1952 c. BOSSMEYER 2,513,938

BACK-SPACING MECHANISM Filed Sept. 13, 1947 4 Sheets-Sheet 2 IIIHHH] lWW" I I l r l r l I i r I l HHlis.

'INVENTOR Charles Bossme er Oct. 14, 1952 c. L. BOSSMEYER 2,613,933

BACKSPACING MECHANISM Filed Sept. 15. 1947 4 Sheets-Sheet 3 iOO TTEJL.

INVENTOR 94 v Charles L. ,Bagsmeyer se Al IIIII 'IIIIII);

ATTOR EYS Patented Oct. 14, 1952 Charles L. Bossmeyer, Rockford,--Ill.,assignor to Dictaphone Corporation, Bridgeport, Conn., a corporation ofNew York Application September 13, 1947, Serial No. 773,823

4 Claims.

This invention is described in relation to variable speed soundreproducing equipment and in such equipment more particularly to acommercially practicable backspacing construction by which the soundreproducing element may quickly and automatically be caused to assume aposition from which to repeat a predetermined amount of the recordingbeing reproduced. Recording and reproducing equipment generally is wellknown and has commonly been used by typists and the like while makingwritten transscriptions of recorded material. Sometimes while makingsuch transcriptions it becomes necessary to have repeated a briefportion of the recording. I am aware that various backspacing mechanismsfor accomplishing such repetitions have heretofore been offered. I havedevised a novel power transmitting construction which is ideally suitedto rapid performance of intermittently desired backspacing operationsand which is readily adaptable to other applications which will suggestthemselves to those skilled in the art of mechanical power supply andtransfer.

In United States Patent No. 2,318,828 to Yerkovich and No. 2,371,116 toYerkovich et al. there are described certain generally similar machinescapable of recording on an endless belt of paperthin pliable plasticmaterial and of reproducing the recordings made on such belts. Duringrecording, one of these belts is stretched between a pair of pulleys, ormandrels, each of a diameter of about 2 in. in the illustrativeembodiments, mounted for rotation about substantially parallel,horizontally disposed axes spaced about 2% in. apart. One of the twom'andrels is driven and is known as a drive mandrel; the other is freeto rotate about its axis and is known as an idler mandrel. The idlermandrel is yieldably mounted so as to hold the recording belt under asmall amount of tension against the surface of the drive mandrel.

In the above-mentioned Yerkovich et al. patent the mandrel axes ofrotation are disposed in substantially the same horizontal plane. Asound recording head and a sound reproducing head are independentlyassociated with the mandrels for movement through independent paths,parallel to the axes of the mandrels and transversely with respect tothe path followed by the surface of the recording belt. Thus a stylusheld in the recording head is enabled to impress a sound groove onto themoving belt. And as the belt moves, the recording head is movedtransversely at a low constant speed across the surface of the belt sothat the groove begins at one side 2 edge of the belt and proceedsaround and around the belt and finally ends at the other side edge ofthe belt. The speed ratios, between linear velocity of a point on thesurface of the belt and linear velocity of the recording head as ittravels transversely with respect to the movement of the belt, are suchthat the belt makes 200 complete revolutions while the stylus movestransversely a distance of one inch. Thus the surface of the recordingbelt, after a sound groove has been impressed upon it, bears asuccession of closely spaced loops the distance from the bottom of onegroove trough to the bottom of the next adjacent groove trough beingapproximately .005 in.;

It is apparent, of course, that the closer the spacing of the loops ofthe sound groove the greater the number of loops that may be containedon a belt of a given size and accordingly the greater the amount ofrecorded material that may be impressed upon that belt. Mechanicalcomplications and the finite width of the sound groove per se set apractical limit upon the closeness of adjacent loops.

In the embodiment disclosed in the Yer'kovich patent the linear velocityof a point on "the recording belt during normal reproducing is disclosedas being on the order of 20 feet per minute. Thus, in ordinary usage,when the auditor who is listening to the recording misses a word or aphrase, she probably will not want a greater amount repeated than iscontained in a single sound groove loop on the recording belt. And ifthe auditor backspaces the reproducing head with respect to the surfaceof the recording belt a distance, for example, of as much as & of aninchit results that she has backspaced a matter of ten sound groove loops,which is surely very much more than she wants repeated. An error inbackspacing movement of as much as in. will result in a repetition oftwice as much as the auditor intends.

Another complication is introduced by the fact that these machines arecommonly used to record a message at a point of origin, to relay themessage over a communication channel to a point of destination and thereto rerecord the message and repeat it to a transcriber or auditor. Forcoding purposes, and to make the most efficient use of the communicationchannel, it is the regular practice to transmit the recorded materialover the channel at a rate several times greater than that at which therecording was made. In order to accomplish such transmission themachines are equipped with variable speed motors having a range on theorder of 10:1. Thus, a

conversation or message recorded at a rate of 150 words per minute mightbe transmitted at a rate of 1000 words per minute. And the machine atthe point of destination must be capable of rerecording at such higherrate and reproducing for transcribing purposes at a rate even below thatof the original.

It is obvious that where backspacing accuracy must bein terms of a fewthousandths of an inch, the speeds of movement of the parts must bebelow certain limits or their inertia, Will introduce such variances asto render the mechanism undependable. And if the structure is designedfor efficient operation at the higher motor speeds, a disproportionateperiod of time will be consumed by each operation when the motor isrunning at lower speeds. Thus, whereas a backspacing operation completedin one half a second might be wholly satisfactory to a typist, a delayof even two secondsonly a 4:1 reduction in motor speed-might after aperiod of transcribing become an excessive annoyance. A reduction on theorder of 4:1 for transcribing would not be unusual in the routineconduct of business quite apart from the channel transmissioncapabilities of the equipment.

Accordingly it will be understood that a satisfactory backspacingmechanism for a modern machine such as referred to not only mustaccurately backspace within a few thousandths of an inch but it mustperform its function without appreciable passage of time regardless ofthe speed setting of the main motor or drive mandrel.

Various mechanisms have been suggested and tried in the past foreffecting automatic backspacing under such circumstances. I have devisedan automatic backspacing construction which will consistently move thereproducing head backwardly with respect to the recording belt adistance of .005 in., or whatever distance may be required for a givenmachine, and which does so in a negligible time regardless of the numberof revolutions per minute being turned by the variable speed drivemotor.

I shall describe my invention as it may be applied to a reproducingmachine of the general type disclosed in the Yerkovich et al. patent.Accordingly, in-my illustrative embodiment, backspacing of one soundgroove will require a transverse movement. of the reproducing head equalto the spacing between adjacent sound groove loopswhere there are twohundred loops to the inch. It is to be noted that the illustrativeembodiment of the Yerkovich et al. patent is a recorder-reproducer; forsimplicity and to avoid repetition the machine which I have selected toexemplify my invention is a reproducer only.- Machines which will beused only for reproducing omit those parts which are required only forrecording. i

It is an object of my invention to provide a device of the characterdescribed having to a notable extent the characteristics andcapabilities set forth. Another object is to produce a commerciallypracticable backspacing mechanism which is operable upon demandindependently of the main motor drive. A further objective is theprovision of a backspacing structure which is both feasible inmanufacture and foolproof in operation and which will consistently givethe desired extent of backspacing. A further object is to provide anovel sort of gear train mechanism which is useful in turning a shaftthrough a given angle upon demand. An-

other object is to provide a multiple gear mechanism wherein a certainportion of the gear train may be meshed or unmeshed at will,automatically and without any possibility of jamming the gears which arecaused to mesh. Yet a further objective resides in the provision of abackspacer and a gear assembly of general utility which overcome certaindisadvantages inherent in the backspacers and gear assemblies of theprior art. Other objectives will be in part pointed out as thedescription proceeds and will in part become apparent therefrom.

The invention accordingly consists in the features of construction,combinations of elements, methods of operation, and arrangements ofparts as will be exemplified in the structure and sequences and groupsof related steps to be hereinafter described and the scope of theapplication of which will be set forth in the accompanying claims.

In this specification and the accompanying drawings I have shown anddescribed a preferred embodiment of my invention and suggested variousmodifications thereof; but it is to be understood that these are notintended to be exhaustive nor limiting of the invention but, on thecontrary, are given for purposes of illustration in order that othersskilled in the art may fully understand the invention and the principlesthereof and the manner of applying it in various forms, each as may bebest suited to the conditions of a particular use.

In the drawings: Figure 1 is a rear elevation (taken along the line llof Figure 2) of a sound reproducing machine of the type disclosed in theYerkovich et al. patent and in which my invention has been incorporated;

Figure 2 is a plan view (taken along the line 2-2 of Figure 1) of themachine;

Figure 3 is a sectional end view taken along the line 33 of Figure 1;

Figure 4 is a fragmentary view on an enlarged scale of a friction clutchassembly which is employed in the machine; 7

Figure 5 is a fragmentary view on an enlarged scale of a mutilated gearassembly which forms a part of the invention;

Figure 6 is a fragmentary sectional view taken along the line B6 ofFigure 5;

Figure 7 is a fragmentary View taken along the line 1-1 of Figure 1showing a part of the backspacing gearing and related mechanisms;

Figure 8 is a sectional view taken along the line 8-8 of Figure 7;

Figure 9 is a fragmentary sectional view taken on an enlarged scalealong. the line 99 of Figure 1; and

Figure 10 is a diagrammatic representation of certain of the electricalcircuits and some of the parts related thereto.

The machine shown in Figure 1 includes a machine frame 20, which maytake the form of a metal casting, and which includes a supporting plate22 rising from its right-hand end (see Figure 1) and a supporting plate24 rising from its lefthand end. A relatively heavy fly wheel 26 isdisposed in a substantially vertical plane at one end of the machine forrotation about a horizontal axis. Fly wheel 26 is driven by a pair ofbelts 28 For a more complete disclosure of the motor arrangement and ofother conventional aspects of the present embodiment not otherwisedetailed herein reference should be made to the disclosure of Yerkovichet al. Patent No. 2,371,116.

The fly wheel is mounted upon a fly wheel shaft 33 (see Figure 1)journaled in supporting plate 22 and carried by the machine frame. Drivemandrel 32 is turned by means of fly wheel shaft 30; since the motorwhich drives the fly wheel is of the variable speed type the rate atwhich the drive mandrel is turned is variable in accordance with themotor speed. Ordinarily a constant speed is used throughout any onerecording, variations in speed being employed for transcribing purposesto pace the rate of reproduction to the optimum capacity of the typistor auditor. An idler mandrel 34 (see also Figure 2) is disposed'for freespect to the path through which the belt moves' The reproducing carriageis slidable upon a horizontally disposed carriage guide rod it (seeFigures land 2) held between supporting plates 22 and 24'. The carriageis caused to slide along the carriage guide rod by a feed screw t2 (seeFigure l) positioned in conventional manner within the guide rod. Theaxis of the feed screw is substantially coextensive with the axis of thecarriage guide rod. A feed nut, not shown but held within the carriage,meshes constantly with the feed screw so that rotation of the screw ad"vances or backspacesthe carriage with respect to the recording beltdepending upon the direction of rotation of the feed screw.

In normal transcribing the feed screw is driven from the fly wheel shaftby a gear train mechanism, to be described. Feed screw G2 is identicalto the feed screw used with the recording carriage.

Hence the reproducing carriage is advanced across themoving belt at arate which makes it possible for the reproducing stylus to followexactly the sound groove which was embossed in the belt by the recordingstylus. In the described embodimentthe feed screw is rotated through120' der es while the recording belt is making one revolution.Accordingly, in 'order to backspace one'soundgroove, the feed screw willhave to be reversed through an angle of 120 degrees.

As shown in Figure 3, fly wheel shaft 30 drives a fly wheel gear dd heldin mesh with an intermediate gear is on an intermediate shaft 48. Gearismaintained in meshing relationship with a second intermediate gear 59which turns a pinion 52 constantly meshed with a feed screw gear 541;The efiect of this gear train is to reduce the numberof revolutions madeby the feed screw gear as compared to the number of revolutions made bythe fly wheel shaft.

The drive relationship between feed screw gear 54 and feed screw 42 isnot positive. As shown in Figure 4, feed screw gear 54 has secured toits inner face an annular rim 56. This rim may be removed, if need be,by unscrewing machine screws 58. A drive flange til is keyed in drivingrelationship to feed screw 4 2; feed screw gear 5 is freely rotatableupon a hub 62 of drive flange 6i). Feed screw gear 5& is held inposition upon hub 62 by rim 56, which overlaps peripheral portions M offlange 6i Feed screw gear 54 may be removed by removing machine screws58 so that the gear can be separated from annular rim 56.

A spider spring 86 is also rotatably positioned on hub 62 and isnormally compressed between the opposing faces of the inside of gear 54and the outside of flange 60. Thus the spider spring tends to push gear56 axially oif of hub 62 but rim 56 prevents any separation more thanthat shown in Figure 4. Accordingly, feed screw gear 54 is heldrelatively firmly with respect to flange 60 and ordinarily the drivingforce imparted to feed screw gear 54 by pinion 52 is transferred throughflange 60 to the feed screw to cause operative rotation thereof. Thefeed screw is mounted for rotation in a feed screw bearing 68 supportedwithin a bearing bushing 79 conventionally held within carriage guiderod ii). The carriage guide rod, as pointed out previously, isnonrotatably fixed between supporting plates 22 and 24.

In the present embodiment, as disclosed in Figure 3, I provide a smallself-starting motor 72 (see also Figures 1 and 8) this motor I use, aswill be described, to effect reverse rotation of the feed screw. Themotor (see Figure '7) drives a spur gear i i mounted upon a motorcountershaft it which drives a bevel gear 18 held in meshingrelationship with a bevel gear 83 which gear in turn is locked to anddrives a shaft 82 (see also Figure 3). A gear 84 driven by shaft 32 isin mesh with and drives an intermediate gear 85 which in turn mesheswith and drives a spur gear 88. which is broken away in Figure 3 to showgear 83 juxtaposed thercbehind) is disposed coaxially with respect togear 83 and is rotated thereby.

Mutilated gear 9!) is arranged to mesh with an intermediate gear 92which gear is in mesh with a backspacing gear 9 solidly secured toflange (it (see also Figure 4). During ordinary operation of thetranscribing equipment a mutilated portion of gear fit, as will bedescribed, faces gear 92 so that there is no driving relationshiptherebetween and accordingly feed screw 62 is driven through thefriction clutch between gear 5% and flange fill. However, when it issought to effect a backspacing operation, the small electric motor '12is energized, as will be described, and the train of gears includingmembers i6, i8, 88, 8 1, 85 and 83 comes into operation to movemutilated gear so into meshing relationship with gear 92 tocause reverserotation of backspacing gear 8 t. During the reverse movement of gear 94the main machine motor continues to drive the fly wheel and accordinglya slipping occurs between flange Gil (now moved by gear 9d) and gear 55(driven from the fly wheel). The energization of motor i2 is of limitedand predetermined duration, as will be developed hereinafter, sothat'thereverse movement of backspace gear 94 extends through degrees.As will be described, gear 92 is then again unmeshed from mutilated gear90.-

It is to be observed that the fly wheel turns at its ordinary speedwhether a backspacing operation is occurring or not and accordingly thetrain of gears which ordinarily drives the feed screw continues tooperate at its normal rate of speed. When a backspacing operation iscalled for, however, the drive is broken at the frictional coupling andthe backspacing mechanism takes precedence as it meshes with moving gear92 to effect the intended backspacing operation.

Because normal fly wheel operation is uninterrupted some provision mustbe made for enabling the backspacing mechanism to be meshed into thedrive to the feed screw. Since there is no interruption of the main.motor, it is obvious that ordinary gearing, Geneva mechanisms, and

A mutilated gear $30 (a part of the like would jam unless the engagingparts happened by chance to fall into mesh. It is equally evident thatthe backspacing movement must be of a measured amount which caninvariably be imposed at will upon the normal drive and which will beindependent of the speed adjustment at which the normal drive isrunning. I have discovered that the mutilated gear may be made to meshproperly with gear 92 each time power is supplied to the backspacermotor by providing the mutilated gear with a flexible feeler 95 which isclamped in place by a clamp screw 98 on the peripheral portions of gear90. The feeler is formed in the present embodiment from stifi wiresimilar to piano wire and has a cross sectional diameter which isapproximately equal tothe chordal thickness of one of the teeth of themutilated gear. The feeler is provided at its outer end portion with adetent I formed by a right angle bend in the wire. The axis of thisdetent is substantially parallel to the axis of rotation of the gear.The feeler is so adjusted and held in place by clamp screw 98 thatdetent I00 occupies approximately the region in space that would beoccupied by the working part of a tooth of gear 90 if there were anothertooth beyond tooth I02. Actually, the detent is adjusted so as to extendslightly beyond the outside diameter of the toothed portion of themutilated gear. In addition, the detent is spaced from tooth I02slightly more than the normal spacing between two adjacent gear teeth.The location shown of clamp screw 93 with respect to tooth I02 and theconfiguration of feeler 99 are such that as the mutilated gear rotatestoward meshing relationship with gear 92, the first contact made isbetween detent I00 and some tooth portion of gear 92. With thearrangement shown, the inherent flexibility of feeler 96 is such thateven if the detent should in the first instance be squarely abuttedagainst an outer end of a tooth, the detent will yield inwardly towardthe center of the mutilated gear and, as the approaching gears tend tomove at diiferent peripheral rates, will find its way into the solidline position illustratedin Figure 6 between two of the teeth of gear92. When the detent assumes the location illustrated, gears 90 and 92are oriented so that the rigid teeth will mesh perfectly. Thus, nomatter what the angular relationships between and peripheral speeds ofthe umneshed gears may be, when a driving force of rotation is appliedto the mutilated gear, feeler 96 and detent I00 automatically align theteeth of gears 90 and 92 so that they are brought into proper mesh. Gear90 is relieved by a clearance groove I04 across its edge into which thedetent may upon occasion enter.

When a backspacing operation is called for, the feed screw must beturned backwardly rapidly through 120 degrees. Hence, gear 92 must ber0- tated through a finite number of degrees and to do this there mustbe a certain number of teeth in the toothed portion of the mutilatedgear in order that gear 92 shall be turned through the correct angle. Inthe embodiment here described (see Figure 3) the mutilated gear isprovided with two toothed portions, each portion having ten teeth, andeach portion is provided with an advance feeler 96 carrying a detent I00. The detent serves as an additional tooth, making eleven operativeteeth on each side of the gear. And the mutilated gear must be turnedthrough 180 degrees to bring the eleven effective teeth of one of itstoothed portions into and out of mesh with the opposing teeth of gear 92so as to turn the feed screw backwardly through 120 degrees. Thus with asingle backspacing operation, eleven teethof gear 92 are caused toreverse the direction of normally ineffective backspacing gear 94 (seealso Figure 4). The friction clutch between feed screw gear 54 andbackspacing gear 94 has a damping effect on any overrunning which mightotherwise occur from the inertia of the parts so that when the eleventeeth of gear 92 have done their work there is a clean break from thebackspacing movement and gear 94 now finds itself displaced backwardlythrough the friction clutch an accurately measured, predeterminedamount. The feed screw also, of course, has been turned back through thesame measured amount. The overall time cycle required for a completeoperation and the amount of feed screw reverse displacement remainconstant under all conditions and are accomplished independently of thespeed at which the variable speed motor is turning.

The backspacing gear train is such that for one-half a revolution ofcountershaft I6 there follows a one-half revolution by the mutilatedgear. One end of countershaft I6 carries a timing cam I06 (see Figure 8Cam I06 is provided with a pair of diametrically spaced dwells I08.During ordinary transcribing operation, a foot IIO of a normally openshort travel limit switch II2 occupies the space within one of the camdwells I08. When the backspacer motor circuit is closed, however, andcountershaft I6 is caused to rotate, the rise on cam I06 comes intoengagement with foot H0 and switch II2 closes a holding circuit which,once closed, remains closed until motor "I2 has turned countershaft 16through 180 degrees again to present a dwell I08 to foot IIO so as toenable holding switch II2 to open and de-energize the backspacer motorcircuit. Thus, a momentary closing of the backspacer motor circuitsuflices to initiate movement of countershaft 16 and thereafter, throughthe action of holding switch I I2, the backspacer motor continuesautomatically to operate the exact length of time required not only toturn countershaft I6 through 180 degrees but also to turn mutilated gearthrough 180 degrees and accordingly to turn feed screw 42 backwardlythrough degrees. During such operation of the backspacer motor and byvirtue of the frictional coupling which is incorporated in the variablespeed motor drive to the feed screw the variable speed motor continuesto operate. As soon as the backspacer motor has caused the feed screw toreverse through 120 degrees ordinary transcribing motion is restored tothe feed screw automatically and without pause.

When feed screw 42 is reversed, reproducing carriage 38 is caused tomove to the left, as shown in Figure 2, by one sound groove loop. It isdesirable that the reproducing stylus which ordinarily rides in thesound groove be lifted from the surface of the recording medium whilethe reproducing carriage is being backspaced. Accordingly I providemechanism which automatically synchronizes with a backspacing operationto lift the stylus of the reproducing carriage off of the surface of therecording medium at the beginning of a backspacing operation and to setit down gently at the end of a backspacing operation.

As shown in Figure 3, gears 88 and 90 are located upon a shaft I I4 (seealso Figure 2). This shaft includes an extended portion II 6 whichreaches behind reproducing carriage 38 even when this carriage is in itsextreme right-hand position.

' Portion H throughout its length behind the path of travel of thereproducer carriage has a non-circular cam-like cross section (see alsoFigure 9). The reproducer carriage is provided with a bracket IIB '(seeFigure 9) which includes an opening I2!) through which cam-like portionIII; extends. Bracket IIB serves as a pivot support for a bell cranklever I22 (see Figure 9) normally urged by gravity in a counterclockwisedirection so that its upper arm I24 bears slidably upon the flatvertical face of portion IIii as the reproducing carriage is moved by.the feed screw during normal operation. However, when a backspacingoperation is instituted and shaft 2 I4 and itscamlike portion Ht arecaused to turn, bell crank lever I22 is caused to rotate through a smallangle in a clockwise-direction and is there held until portion I I5 isturned through 180 degrees. While the bell crank lever is held againstgravity in its clockwise position, its other arm I26 is raised somewhatfrom the position illustrated in Figure 9 and in its raised position itis in lifting contact with the underside, of the bottom edge oftransducing cartridge I28 of the reproducing carriage. The stylus isconventionally mounted in this cartridge and is held elevated slightlyoff the recording medium during the period while bell crank lever 522occupies its clockwise position. It is during this period that the feedscrew is rotated backwardly. This construction obviously raises andlowers the stylus with a smooth, gentle motion which cannot damage thedelicatepoint.

As shown in Figure 8, a normally closed low travel limit switch Hit isfixed in position near switch II2 with its switch-throwing button I32 sodisposed as to be engaged and actuated by the head of a screw I34 (seeFigure 2) mounted in the left-hand face of the reproducing carriage. Theposition of screw I34 with respect to the reproducing carriage may beadjusted and locked by an adjustment nut I36. Thus, when carriage 3B ismoved to its most left-hand position at the beginning of a reproducingoperation, screw I3 1 is brought into contact with button I32 so as toopen switch I33. With switch I30 open the circuit. of the backspacingmotor is open so that a backspacing operation cannot be instituted;

.switch liiiiwill not close until the reproducing carriage is moved fromits most left-hand position. In this manner it is made impossible forthe backspacing motor to be energized unless the reproducing carriage isin a position from which it may be backspaced without jamming.

Figure indicates diagrammatically the electrical circuit of thebackspacing motor. As here shown, a backspacing operation is institutedby momentarily closing a normally open switch I38. Ordinarily thisswitch is arranged for foot operation. When switch I33 is closed currentflows from a supply line I i-Il through a branch line I42, switch I33,normally closed safety switch I38, and branch lines EM and Hit intomotor I2, thence to a branch line H58 and back to main line I553. Whenswitch 333 is closed motor I2 starts and cam Hit immediately operates toclose holding switch IIZ. Power is then available through branch lineits to branch line Hi6 and thence through the motor and line MS to lineI50. Thus, when the starting switch is closed, holding switch II2assures that a complete backspacing operation is accomplished. When thereproducing carriage is moved to its most left-hand position, however,screw ifi l comes into contact with button I32 and opens switch I30. Aslong as switch I3B is open nothing is accomplished by closing switch I38and so backspacing is'prevented until such time as thereproducingcarriage is moved to a position from which it may bebackspaced without jamming. i

From the foregoing it will be seen that a backspacing structure made inaccordance with the present invention is well adapted to attain the endsand objects hereinbeforeset forth and to be economically manufacturedsince the several parts and assemblies are suited to common productionmethods and are susceptible to a wide latitude of variations as may bedesirable in adapting the invention to different applications.

As various embodiments may be made of the above invention and as changesmight be made in the embodiment above set forth, it is to be understoodthat all matter hereinbefore set forth or shown in theaccompanying'drawings is to'be interpreted as illustrative and not in alimiting sense.

I claim: I v

1. In adjustable speed sound reproducing equipment of the type wherein atranslating element follows a continuous sound track disposed in closelyspaced loops on the surface of a driven recording medium: a reproducercarriage mechanism in which the translating element is'supported, themechanism being disposed for travel along a path transverse with respectto the direction of the sound track loops, a feed screw'meshed with themechanism and rotatable to advance-or backspace it along the path, anadjustable speed motor and drive connected to rotate the feed.

screw at a selected speed in the direction-which advances the mechanism,ahigh speed backspace motor and drive, an intermediate mechanismdisposed between the backspace drive and the feed screw and operable bythe backspace-drive to rotate the feed screw in the other direction-anda control system regulating energysupply'to the I motors; said systemincluding a normally'closed supply line to the adjustable speed :motor,a normally open supply line to the backspace-motor, a switch in thebackspace supply-line for closing the circuit therethrough, a normallyopen holding switch in parallel around the closing "switch, and acoupling arranged to close"th'e holding switch'when the backspace:r'notor is energized and to hold it closed through a predeterminedbackspace motor movement. Y 2. In adjustable speed sound reproducingequipment of the type wherein a translating element follows a continuoussound track disposed in closely spaced loops on the surface of a drivenrecording medium: a reproducer carriage mechanism in which thetranslating element is supported, the mechanism being disposed fortravel along a path transverse with respect to the direction of thesound track loops, a feed screw meshed with the mechanism and rotatableto advance or backspace it along the path, a drive unit including aportion positively coupled to the feed screw, a high inertia typerecording medium supporting and driving assembly associated with saidreproducer carriage mechanism for moving the recording medium withrespect to said path, an adjustable speed motor having a range of fromlow speed to a high speed at least several times that of the low speedcoupled to said recording medium assembly, a power take-01f assemblycoupled to said recording medium assembly and in drivable relationshipwith said drive unit to rotate the feed screw at a selected speed in adirection which advances the mechanism, a backspace motor of high speedas compared to the lower speeds of said adjustable speed motor and lowinertia as compared to said supporting and driving assembly, said motorbeing disposed adjacent said feed screw and directly and positivelyengageable upon demand with said drive unit to rotate the feed screw inthe other direction independently of the operation of said adjustablespeed motor, and a backspace control assembly operative between saidbackspace motor and said drive unit predetermining the drive of saidbackspace motor upon initiation of a backspace operation.

3. In sound reproducing apparatus of the type wherein a translatingelement follows a con-. tinuous sound track disposed'in closely spacedloops on the surface of a recording medium, in combination: a variablespeed reproduce drive motor effectively variable in speed through arange of from low speed to a high speed of at least several times thatof the low speed, reproduce drive mechanism actuated by the drive motorand coupled to produce relative movement between the translating elementand recording medium, a backspace drive motor having an effective speedsubstantially higher than the lower speeds at which said reproduce drivemotor may be run, backspace drive mechanism actuated by the backspacemotor and coupled to effect a backspacing movement of the translatingelement with respect to the recording medium, said reproduce drive motorbeing supplied with power normally to run without interruption at anadjusted speed, said backspace drive motor being supplied normally withpower only when a backspacing movement is demanded, each of said drivemechanisms being disposed in driving relationship to a common drivenmember, the drive between said backspace motor and said driven memberincluding a segmental gear normally out of mesh with but in drivablerelationship to another gear effective upon said driven member, and abackspace control assembly operative between said backspace drive motorand said driven member predetermining the drive of said back space drivemotor upon initiation of a backspace operation.

4. In sound reproducing apparatus of the type wherein a translatingelement follows a continuous sound track disposed in closely spacedloops on the surface of a recording medium, in

combination: a variable speed reproduce drive motor effectively variablein speed through a range of from low speed to a high speed at leastseveral times that of the low speed, reproduce drive mechanism actuatedby the drive motor and coupled to produce relative movement between thetranslating element and recording medium, a backspace drive motor havingan effective speed substantially higher than the lower speeds at whichsaid reproduce drive motor may be run, backspace drive mechanismactuated by the backspace motor and coupled to effect a backspacingmovement of the translating element with respect to the recordingmedium, said reproduce drive motor and mechanism incorporating a highmoment of inertia compared to that of the backspace drive motor andmechanism and being supplied with power normally to run Withoutinterruption at its adjusted speed, said backspace drive motor beingsupplied normally with power only when a backspacing movement isdemanded, each of said drive mechanisms being disposed in drivingrelationship to a common driven member, said driven member being part ofan assembly operative to effect relative movements of the translatingelement with respect to the recording medium, whereby such relativemovement caused by the backspace drive motor occurs at a rate which ishigh as compared to relative movement caused by the reproduce drivemotor when adjusted to a relatively low speed in its range, and abackspace control assembly operative between said backspace drive motorand said driven member predetermining the drive of said backspace drivemotor upon initiation of a backspace operation.

CHARLES L. BOSSMEYER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 694,784 Ramsay Mar. 4, 19022,145,498 Stockton Jan. 31, 1939 2,277,208 Chenoweth et a1. Mar. 24,1942 2,284,043 Clausen May 26, 1942 2,318,828 Yerkovich May 11, 19432,340,658 Goldman Feb. 1, 1944 2,359,255 Smith Sept. 26, 1944

